• 한국농공학회지
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• 제42권6호
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• pp.56-62
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• 2000

The NRCS curve number (CN) method has been widely adopted in practice to synthesize runoff hydrographs from small watersheds with complex land use. It may not be valid to apply this model for irrigated paddies, since hydrological characteristics of irrigated rice paddies are not sufficiently considered in CN method. This paper attempts to extend the capability of the well-known SCS TR-20 model to local conditions by formulating a submodel for the runoff-processes in paddies. The modified model was tested with field data from the Baran watershed. The results were in good agreement with field data. It was also applicable to simulate runoff changes resulting from land use changes within the watershed.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(1)
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• pp.42-43
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• 2005

• 한국관개배수논문집
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• 제13권2호
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• pp.274-282
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• 2006

The objective of this study was to develop a hydrologic simulation model to predict daily streamflow from a small agricultural watershed considering irrigation return flow. The proposed IREFLOW(Irrigation REturn FLOW) model consists of hillslope runoff model, irrigation scheme drainage model, and irrigation return flow model, and simulates daily streamflow from an irrigated watershed. Two small watersheds were selected for monitoring of hydrological components and evaluating the model application. The relative error (RE) between observed and simulated daily streamflow were 2.9% and 6.4%, respectively, on two small agricultural watersheds (Baran and Gicheon) for the calibration period. The values of RE in daliy streamflow for the validation period were 6.0% for the Baran watershed, and 2.8% for the Gicheon watershed.

• 한국농공학회논문집
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• 제51권5호
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• pp.35-49
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• 2009

This study proposes a method to evaluate agricultural reservoirs drought by modifying SWSI (Surface Water Supply Index). The method was applied to Geum river basin and the results were represented as spatially distributed information. The SWSI evaluates hydrological drought of watershed unit by selectively applying one or all of the components of snowpack, precipitation, streamflow and reservoir storage. South Korea has 22 % of agricultural area, and rice paddy covers 64 % among them. Usually paddy fields scattered along stream are irrigated by so many small agricultural reservoirs. It is difficult to evaluate agriculture drought by the little information and large number of agricultural reservoirs. In this study, seven agricultural reservoirs over 10 million ton storage capacity were selected in Geum river basin, and the SWSI was evaluated for both upstream and downstream of the reservoirs using 16 years data (1991-2006). Using the results, multiple regression analyses with precipitation and reservoir storage as variables were conducted and the equations were applied to other watersheds. The spatial results by applying regression equations showed that the severe and moderate drought conditions of July and September in 1994, June in 1995, and May in 2001 were well expressed by the watershed unit.

• 한국농공학회논문집
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• 제63권2호
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• pp.85-96
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• 2021

Irrigation return flow is defined as the excess of irrigation water that is not evapotranspirated by direct surface drainage, and which returns to an aquifer. It is important to quantitatively estimate the irrigation return flow of the water cycle in an agricultural watershed. However, the previous studies on irrigation return flow rates are limitations in quantifying the return flow rate by region. Therefore, simulating irrigation return flow by accounting for various water loss rates derived from agricultural practices is necessary while the hydrologic and hydraulic modeling of cultivated canal-irrigated watersheds. In this study, the irrigation return flow rate of agricultural water, especially for the entire agricultural watershed, was estimated using the SWMM (Storm Water Management Model) module from 2010 to 2019 for the Madun reservoir located in Anseong, Gyeonggi-do. The results of SWMM simulation and water balance analysis estimated irrigation return flow rate. The estimated average annual irrigation return flow ratio during the period from 2010 to 2019 was approximately 55.3% of the annual irrigation amounts of which 35.9% was rapid return flow and 19.4% was delayed return flow. Based on these results, the hydrologic and hydraulic modeling approach can provide a valuable approach for estimating the irrigation return flow under different hydrological and water management conditions.

• 한국농공학회논문집
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• 제48권2호
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• pp.13-23
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• 2006

In Korea, upland irrigation generally depends on the ground water or natural rainfall since irrigation water supplied from dams is mainly used for paddy irrigation, and only limited amount of irrigation water is supplied to the upland area. For the stable security of upland irrigation water, storage level of irrigation dams was simulated by the periods. A year was divided into 4 periods considering the irrigation characteristics. Through the periodical management of storage level, water utilization efficiency in irrigation dams could be enhanced and it makes available to secure extra available water from existing dams without new development of water resources. Two study areas, Seongju and Donghwa dam, were selected for this study. Runoff from the watersheds was simulated by the modified tank model and the irrigation water to upland crops was calculated by the Penman-Monteith method. The analyzed results showed that relatively sufficient extra available water could be secured for the main upland crops in Seongju area. In case of Donghwa area, water supply to non-irrigated upland was possible in normal years but extra water was necessary in drought years such as 1998 and 2001.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.516-516
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• 2022

Agricultural reservoirs are critical water resources structures to ensure continuous water supplies for rice cultivation in Korea. Climate change has increased the risk of reservoir failure by exacerbating discrepancies in upstream runoff generation, downstream irrigation water demands, and evaporation losses. In this study, the variations in water balance components of 400 major reservoirs during 1973-2017 were examined to identify the reservoirs with reliable storage capacities and resilience. A conceptual lumped hydrological model was used to transform the incident rainfall into the inflows entering the reservoirs and the paddy water balance model was used to estimate the irrigation water demand. Historical climate data analysis showed a sharp warming gradient during the last 45 years that was particularly evident in the central and southern regions of the country, which were also the main agricultural areas with high reservoir density. We noted a country-wide progressive increase in average annual cumulative rainfall, but the forcing mechanism of the rainfall increment and its spatial-temporal trends were not fully understood. Climate warming resulted in a significant increase in irrigation water demand, while heavy rains increased runoff generation in the reservoir watersheds. Most reservoirs had reliable storage capacities to meet the demands of a 10-year return frequency drought but the resilience of reservoirs gradually declined over time. This suggests that the recovery time of reservoirs from the failure state had increased which also signifies that the duration of the dry season has been prolonged while the wet season has become shorter and/or more intense. The watershed-irrigated area ratio (W-I_ratio) was critical and the results showed that a slight disruption in reservoir water balance under the influence of future climate change would seriously compromise the performance of reservoirs with W-I_ratio< 5.

• 한국토양비료학회지
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• 제39권4호
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• pp.237-244
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• 2006

한반도 통일 후 식량 안보와 수자원 확보를 위해 추진되어 오고 있는 새만금 간척 사업 완공 후 담수호 수질보전을 위해서는 오염 물질 관리의 우선순위 설정에 의한 토지 이용 계획 수립이 필요하다. 새만금 유역에서 오염 물질 부하를 경감시키기 위한 농경지의 역항을 평가하기 위하여 만경강과 동진강 유역에서 오염 부하, 토지 이용 및 분포, 용수 사용을 조사하였다. 만경강 년간 하천수는 700만$m^3$이며, 이중 14.1%는 생활 용수, 73.6%는 농업용수, 12.3%는 산업 용수에서 유래하고 있다. 동진강 하천수는 505백만$m^3$이며 이중 3.0%는 생활 용수, 94.5%는 농업용수, 2.5%는 산업 용수에서 유래한다. 동진강 유역은 만경강 유역에 비해서 농경지 면적 비율은 1.4배, 축산 농지 면적 비율은 7배가 많았고, 임지는 0.74배, 주택지는 0.67배 적었다. 만경강 유역과 동진강 유역의 주요한 오염원은 토지 유래보다도 오히려 생활 하수와 축산 오수로 나타났다. 이같은 용수 사용과 토지 이용은 하천 수질에도 영향을 주어, 동진강 유역은 만경강 유역보다 전기전도도, $BOD_5$, TN 그리고 TP값이 훨씬 낮았다. 동진강 유역은 하천 유역의 논 면적 비율이 높아 축산업 면적이 넓었음에도 불구하고 강우 후 유달 부하량이 훨씬 낮았다. 만경강 지류인 익산천 하천수를 논에 관개 후 150 m 유거 중 침전 및 흡착에 의해 질소는 37%, 인산은 50%, $BOD_5$는 15%가 저감되었으며, 수확기 벼는 ha당 TN 100.0 kg, $P_2O_5$ 24.0 kg, $K_2O$ 119.2 kg을 흡수한 결과로 보아, 새만금 유역에서 벼 재배는 하천 수질 보전에 긍정적 기여를 하고 있다는 것을 알 수 있다.